At the organization of the Nauvoo police (former Danites), Smith authorizes them to kill "if need be" and says his life is endangered by "a little dough-head" and "a Brutus." First Counselor William Law assumes this refers to him. Joseph Smith pronounced a blessing on them and offered to pay twice the amount of any bribe offered to them for information about the briber.
[Quinn, D. Michael, The Mormon Hierarchy: Origins of Power, Appendix 7: Selected Chronology of the Church of Jesus Christ of Latter-day Saints, 1830-47, http://amzn.to/origins-power; BYU Studies Journal, volume 46, no. 4: A Chronology of the Life of Joseph Smith, http://byustudies.byu.edu]